...It provides NAT, port-forwarding, spoofing list, blacklist of crackers and spywares sites, protection for tcp/udp scans, DOS/DDOS and Smurf attacks, TCP tuning, DHCP and PPP support and much more.
Shell daemon I made for maintaining my DSL up back in 2000. As of year 2006, there is probably a lot of good tools for monitoring and keeping alive your ADSL connection, like ddclient for DynDNS, and native Debian PPP management for example...